Three of the following test scores are Cyprian's and the other three are Margaret's: 85, 87, 92, 93, 94, 98. Cyprian's mean score is 90. What is Margaret's mean score?
The sum of all six scores is $549$.  The sum of Cyprian's scores is $3(90)=270$, so the sum of Margaret's scores is $549-270=279$.  Thus the average of her scores is $\frac{279}{3}=\boxed{93}$.